13 cm calling frequency.

VK4AFL · Post by **VK4AFL** » Wed May 08, 2019 3:41 pm

Re recent comments on Facebook [I don`t have an account so cannot post there] about the 13 cm calling frequency don`t even consider 2403.100 MHz as its entirely unnecessary & full of WiFi QRM. 2400.100 is 3 MHz further away from the crud & in my case its the difference between a minimum of an S7 to S9 [+ 20 db depending on antenna heading] noise floor versus S3.

For some reason SE VK4 is slow to grasp this but its getting wider acceptance & the only way to go. 144.100 MHz = 2400.100 MHz in the majority of xvtr`s so that shouldn`t be a problem. QRM aside its an excellent band.

73, Trevor, VK4AFL.

VK3QI · Post by **VK3QI** » Wed May 08, 2019 6:24 pm

Trevor,

There is a problem with your proposal.

2400 - 2403 is set aside as Amateur Satellites according to the recommended band plan, with a note that the satellite section should be kept clear of all terrestrial operations.

That is why 2403.150 has become the de-facto calling frequency in VK3/7 and (presumably) other states as well.

Also 2403.000 - 2403.100 is designated as EME only.

Perhaps you should send a note to the WIA/RASA groups who discuss the band plans to ascertain their view on the matter.

Cheers

Peter VK3QI

VK5ZD · Post by **VK5ZD** » Thu May 09, 2019 12:21 am

In VK5 we use 2400.15MHz or 2400.2MHz.

The band plan is a suggestion, not an actual license condition, and I'm happy follow the band plan where practical. However, as has been noted, there is a lot of WiFi 'crud' around 2403MHz and above. Secondly, the only amateur satellite using 2.4GHz that I'm aware of is QO-100 which is not visible from anywhere in Australia. Therefore, operating on 2400.xMhz is not going to interfere with any satellite operations.

Incidentally, QO-100 has 2 transponders, one 250KHz wide and one 8MHz wide. The uplink frequencies are 2400.05MHz to 2400.30MHz and 2401.5Mhz to 2409.5MHz, so I guess they didn't consult the WIA bandplan when picking these frequencies.

VK3QI · Post by **VK3QI** » Thu May 09, 2019 1:32 am

Fair enough Iain,

Interestingly, in Melbourne the 2403 region is often "quieter" than the 2400 region. It all seems to depend on where the dish is pointed and how many wifi devices are switched on in the immediate area at any particular time.

Often I can see upwards of 10 users just on my laptop sitting at the office desk.

Operating from VK3ER/p which is about 80 kms N/W of Melbourne, as you turn the dish towards Melbourne, the background noise comes up and is pretty well constant right across the 2400 to 2407 range.

I know the guys in Geelong have great difficulty beaming across the bay through the city pretty well right across the frequency range as well.

I will raise the point with some of the other VK3 ops and see what they want to do.

Cheers

Peter VK3QI

VK7HH · Post by **VK7HH** » Thu May 09, 2019 11:56 am

Is there a reason why the 2300-2302 range is not used instead of 2403? Especially for SSB calling.
From the bandplan

The segment 2300 – 2302 MHz is recommended for use in areas where the weak signal segment on 2403
MHz suffers unacceptable interference from digital links and other devices, and also for crossband EME
contacts with overseas stations operating on 2304 MHz.

VK3QI · Post by **VK3QI** » Thu May 09, 2019 12:14 pm

Hayden,

I am not fully aware of the earlier history of using 13cm. (pre-2002), but I do note that 2300 to 2302 is only available to Advanced licences, whereas Standard licences can use 2400- 2450.

The use of 2300 - 2302 was not always available to VK amateurs. Maybe one of the EME enthusiasts can enlighten us about the use of this segment.

Peter VK3QI

VK3QI · Post by **VK3QI** » Thu May 09, 2019 12:36 pm

Hayden,

A bit of background. Likely terrestrial contacts with New Zealand, New Caledonia and Indonesia.

NEW ZEALAND

http://www.nzart.org.nz/assets/bandplan ... ndplan.pdf

JAPAN (EME)

https://jarl.org/English/6_Band_Plan/Ja ... 150105.pdf

FRANCE = PRESUMABLY NEW CALEDONIA AS WELL

http://thf.r-e-f.org/plans_des_bandes/2_3g.htm

INDONESIA

https://www.qsl.net/yb0emj/hamfrq.html

Looking at the Hepburn Charts, I have often wondered just how many qsos could be made between Australia and Indonesia on 2.4 GHz and above from the north west of Australia.

Cheers

Peter VK3QI

VK7HH · Post by **VK7HH** » Thu May 09, 2019 12:51 pm

One of my goals is to try to work ZL on 2.4 GHz one season. Now I'm setup for it, hopefully it will become a reality. Just need the right conditions, and oh, some ZL's at the other end.... too bad we don't have an alternative logger function yet, but hopefully there will be one come summer

which will make things easy.

VK4VU · Post by **VK4VU** » Thu May 09, 2019 10:33 pm

I'd have to agree that adopting 2400.xx work terrestrial weak signal work makes a lot of sense.

As VK5ZD rightly points out, the only amateur satellite that is currently using the band is QO-100 and unfortunately, the footprint doesn't cover Australia.

Whilst its good to have sensible domestic band plans in place, it seems that a pragmatic solution to overcoming excessive interference from WiFi systems is simply use 2400.xx instead of 2403.xxx.

Some time ago, I set out to show why 2400.xx was a better option. For this test I used the following test set-up.

650mm offset feed TV dish with 5T helix feed (as used on my old AO-40 set-up) at 12m AGL > 20m of LDF4-50 cable > DB6NT 2 stage LNA > HP8594E spectrum analyser.

I captured two plots from the spectrum analyser with the trace set to Peak Hold for about 5 minutes. The first shows a 2402 MHz Centre Freq with 4 MHz span, and the second being a 2400 MHz Centre Freq with 20 MHz span. The level is around -50 dBm, so given approx 35 dB gain in the LNA, means that the levels into the RX front end are around -85 dBm, which is much stronger than a weak DX (or may not so far away !) signal.

: 2402 MHz centre frequency - 4 MHz span

: 2400 MHz centre frequency - 20 MHz span

Note that the antenna was pointed at 192 deg from here (i.e right down the street where I live).

The results of this experiment shows that 2400 MHz is a certainly much cleaner than 2403 MHz, and certainly supports the case to keep away from WLAN frequencies.

Given that most transverters are probably set up to cover 2400 MHz anyway using a either a 144 or 430 MHz IF it shouldn't be hard to try both. Frequency agility shouldn't be an issue.

I'm sure that the WIA band-plans were developed with the best of intentions, but in this case it makes no sense to blindly use 2403.xxx when a viable alternative is so easily found.

If there was a subsequent launch of a satellite using 2400.xxx then clearly a review would be needed to find a suitable alternative.

73

Rod VK4VU

VK3QI · Post by **VK3QI** » Thu May 09, 2019 11:48 pm

Rod,

Doesn't your first picture (4302 MHz centre, 4 MHz span) show that 2403 is clear, just like 2400?

The results we have had are relatively similar to yours - that is, the WIFI noise tends to peak on the even frequencies, although the reason for that is not clear.

Peter VK3QI

VK4VU · Post by **VK4VU** » Fri May 10, 2019 6:24 am

Hi Peter,

Certainly there are some peaks and troughs in that plot. I think the key thing to notice though is that around 2400 the plot is basically hitting the noise floor of the measurement system (almost 'flat-lining'), whereas if you look closely in the troughs around say 2402.2 and again at around 2403 they are a bit 'fuzzy' showing that there is some noise present. Measurements aside, I can verify that on my receive system 2400.xx is a much better option that 2403.xx MHz.

BTW I'm not sure myself about why the plots have though peaks and troughs - perhaps an artifact of the modulation ?? I'll have to do some more research to understand why this is so.

The important thing is that if you consider that the lowest WiFi Channel #1 is centred on 2412 MHz, then an IEEE 802.11B compliant signal should be 30 dB down at 2401 MHz (-11 MHz offset). The mask has even more stringent requirements at 22 MHz offset, but then that is outside of our band !

See https://www.researchgate.net/figure/A-t ... _235946397

73

Rod VK4VU

VK3QI · Post by **VK3QI** » Fri May 10, 2019 9:32 am

Rod,

I understand what you are saying and it makes sense if all WiFi equipment was meeting the standard, but as we all know, the denser the population, the more likely you are to find non compliant devices.

Essentially operating from home in Melbourne, 8 kms east of the city, the whole band has "squiggles and pops" over all frequencies as you rotate the dish through 360 degrees. It becomes pot luck to find a frequency that remains clear long enough to make a qso in the required direction.

I had a discussion last night at a local club meeting with some active 2.4 Ghz operators about the pros and cons of moving to 2400. Technically easy to do, but the consensus around here was that the benefit was not that great. I will discuss it further with some more operators over the coming weeks.

Cheers

Peter VK3QI

VK7HH · Post by **VK7HH** » Fri May 10, 2019 10:32 am

I have also had success with a bandpass filter kindly provided by VK3PP.

On 2403.150 I can hear noise and hash from local WiFi crud, but with the BPF inline (20dB down at 2420 I think) the noise is considerably less. Mainly due to the fact that every above Channel 2 is knocked down below 50dB. The upper part of Channel 1 is 20dB down and at 2412 I think it's about 10dB down.

VK3MAT · Post by **VK3MAT** » Sat May 11, 2019 9:08 am

Im pretty sure this was the plot from the filter Hayden. I wonder if it could be dropped in Freq a little more? From memory I had trouble doing that but could be worth another try.

Matt

VK1JA · Post by **VK1JA** » Sat May 11, 2019 9:42 am

G'day Matt/Hayden,

Do you have any links to the design or info on the bpf? Was it homebrew or commercial?

Cheers
Jayson

VK3MAT · Post by **VK3MAT** » Sat May 11, 2019 10:13 am

Hi Jayson

I picked it up at a hamfest so unfortunately I don't have any details on the unit. It's quite a large thing taking up a fair bit of room in the transverse box though.

Matt

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